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bpo-47177: Replace f_lasti with prev_instr (GH-32208)
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@brandtbucher
brandtbucher authored Apr 7, 2022
1 parent 87eec70 commit ef6a482
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Showing 10 changed files with 90 additions and 75 deletions.
17 changes: 10 additions & 7 deletions Include/internal/pycore_frame.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,11 +39,6 @@ enum _frameowner {
FRAME_OWNED_BY_FRAME_OBJECT = 2
};

/*
frame->f_lasti refers to the index of the last instruction,
unless it's -1 in which case next_instr should be first_instr.
*/

typedef struct _PyInterpreterFrame {
PyFunctionObject *f_func; /* Strong reference */
PyObject *f_globals; /* Borrowed reference */
Expand All @@ -52,13 +47,20 @@ typedef struct _PyInterpreterFrame {
PyCodeObject *f_code; /* Strong reference */
PyFrameObject *frame_obj; /* Strong reference, may be NULL */
struct _PyInterpreterFrame *previous;
int f_lasti; /* Last instruction if called */
// NOTE: This is not necessarily the last instruction started in the given
// frame. Rather, it is the code unit *prior to* the *next* instruction. For
// example, it may be an inline CACHE entry, an instruction we just jumped
// over, or (in the case of a newly-created frame) a totally invalid value:
_Py_CODEUNIT *prev_instr;
int stacktop; /* Offset of TOS from localsplus */
bool is_entry; // Whether this is the "root" frame for the current _PyCFrame.
char owner;
PyObject *localsplus[1];
} _PyInterpreterFrame;

#define _PyInterpreterFrame_LASTI(IF) \
((int)((IF)->prev_instr - _PyCode_CODE((IF)->f_code)))

static inline PyObject **_PyFrame_Stackbase(_PyInterpreterFrame *f) {
return f->localsplus + f->f_code->co_nlocalsplus;
}
Expand Down Expand Up @@ -97,7 +99,7 @@ _PyFrame_InitializeSpecials(
frame->f_locals = Py_XNewRef(locals);
frame->stacktop = nlocalsplus;
frame->frame_obj = NULL;
frame->f_lasti = -1;
frame->prev_instr = _PyCode_CODE(frame->f_code) - 1;
frame->is_entry = false;
frame->owner = FRAME_OWNED_BY_THREAD;
}
Expand Down Expand Up @@ -186,6 +188,7 @@ void _PyThreadState_PopFrame(PyThreadState *tstate, _PyInterpreterFrame *frame);
_PyInterpreterFrame *
_PyFrame_Push(PyThreadState *tstate, PyFunctionObject *func);

int _PyInterpreterFrame_GetLine(_PyInterpreterFrame *frame);

static inline
PyGenObject *_PyFrame_GetGenerator(_PyInterpreterFrame *frame)
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-03-31-01-30-03.bpo-47177.fQqaov.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Replace the ``f_lasti`` member of the internal ``_PyInterpreterFrame`` structure with a ``prev_instr`` pointer, which reduces overhead in the main interpreter loop. The ``f_lasti`` attribute of Python-layer frame objects is preserved for backward-compatibility.
2 changes: 1 addition & 1 deletion Modules/_tracemalloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -308,7 +308,7 @@ static void
tracemalloc_get_frame(_PyInterpreterFrame *pyframe, frame_t *frame)
{
frame->filename = &_Py_STR(anon_unknown);
int lineno = PyCode_Addr2Line(pyframe->f_code, pyframe->f_lasti*sizeof(_Py_CODEUNIT));
int lineno = _PyInterpreterFrame_GetLine(pyframe);
if (lineno < 0) {
lineno = 0;
}
Expand Down
35 changes: 18 additions & 17 deletions Objects/frameobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ PyFrame_GetLineNumber(PyFrameObject *f)
return f->f_lineno;
}
else {
return PyCode_Addr2Line(f->f_frame->f_code, f->f_frame->f_lasti*sizeof(_Py_CODEUNIT));
return _PyInterpreterFrame_GetLine(f->f_frame);
}
}

Expand All @@ -58,10 +58,11 @@ frame_getlineno(PyFrameObject *f, void *closure)
static PyObject *
frame_getlasti(PyFrameObject *f, void *closure)
{
if (f->f_frame->f_lasti < 0) {
int lasti = _PyInterpreterFrame_LASTI(f->f_frame);
if (lasti < 0) {
return PyLong_FromLong(-1);
}
return PyLong_FromLong(f->f_frame->f_lasti*sizeof(_Py_CODEUNIT));
return PyLong_FromLong(lasti * sizeof(_Py_CODEUNIT));
}

static PyObject *
Expand Down Expand Up @@ -419,12 +420,11 @@ _PyFrame_GetState(PyFrameObject *frame)
}
case FRAME_OWNED_BY_THREAD:
{
if (frame->f_frame->f_lasti < 0) {
if (_PyInterpreterFrame_LASTI(frame->f_frame) < 0) {
return FRAME_CREATED;
}
uint8_t *code = (uint8_t *)frame->f_frame->f_code->co_code_adaptive;
int opcode = code[frame->f_frame->f_lasti*sizeof(_Py_CODEUNIT)];
switch(_PyOpcode_Deopt[opcode]) {
switch (_PyOpcode_Deopt[_Py_OPCODE(*frame->f_frame->prev_instr)])
{
case COPY_FREE_VARS:
case MAKE_CELL:
case RETURN_GENERATOR:
Expand Down Expand Up @@ -555,7 +555,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore

int64_t best_stack = OVERFLOWED;
int best_addr = -1;
int64_t start_stack = stacks[f->f_frame->f_lasti];
int64_t start_stack = stacks[_PyInterpreterFrame_LASTI(f->f_frame)];
int err = -1;
const char *msg = "cannot find bytecode for specified line";
for (int i = 0; i < len; i++) {
Expand Down Expand Up @@ -598,7 +598,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
}
/* Finally set the new lasti and return OK. */
f->f_lineno = 0;
f->f_frame->f_lasti = best_addr;
f->f_frame->prev_instr = _PyCode_CODE(f->f_frame->f_code) + best_addr;
return 0;
}

Expand Down Expand Up @@ -880,10 +880,11 @@ _PyFrame_OpAlreadyRan(_PyInterpreterFrame *frame, int opcode, int oparg)
// This only works when opcode is a non-quickened form:
assert(_PyOpcode_Deopt[opcode] == opcode);
int check_oparg = 0;
for (int i = 0; i < frame->f_lasti; i++) {
_Py_CODEUNIT instruction = _PyCode_CODE(frame->f_code)[i];
int check_opcode = _PyOpcode_Deopt[_Py_OPCODE(instruction)];
check_oparg |= _Py_OPARG(instruction);
for (_Py_CODEUNIT *instruction = _PyCode_CODE(frame->f_code);
instruction < frame->prev_instr; instruction++)
{
int check_opcode = _PyOpcode_Deopt[_Py_OPCODE(*instruction)];
check_oparg |= _Py_OPARG(*instruction);
if (check_opcode == opcode && check_oparg == oparg) {
return 1;
}
Expand All @@ -893,7 +894,7 @@ _PyFrame_OpAlreadyRan(_PyInterpreterFrame *frame, int opcode, int oparg)
else {
check_oparg = 0;
}
i += _PyOpcode_Caches[check_opcode];
instruction += _PyOpcode_Caches[check_opcode];
}
return 0;
}
Expand All @@ -914,8 +915,8 @@ _PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame) {
fast = _PyFrame_GetLocalsArray(frame);
// COPY_FREE_VARS has no quickened forms, so no need to use _PyOpcode_Deopt
// here:
if (frame->f_lasti < 0 && _Py_OPCODE(_PyCode_CODE(co)[0]) == COPY_FREE_VARS)
{
int lasti = _PyInterpreterFrame_LASTI(frame);
if (lasti < 0 && _Py_OPCODE(_PyCode_CODE(co)[0]) == COPY_FREE_VARS) {
/* Free vars have not been initialized -- Do that */
PyCodeObject *co = frame->f_code;
PyObject *closure = frame->f_func->func_closure;
Expand All @@ -926,7 +927,7 @@ _PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame) {
frame->localsplus[offset + i] = o;
}
// COPY_FREE_VARS doesn't have inline CACHEs, either:
frame->f_lasti = 0;
frame->prev_instr = _PyCode_CODE(frame->f_code);
}
for (int i = 0; i < co->co_nlocalsplus; i++) {
_PyLocals_Kind kind = _PyLocals_GetKind(co->co_localspluskinds, i);
Expand Down
19 changes: 8 additions & 11 deletions Objects/genobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -352,14 +352,14 @@ _PyGen_yf(PyGenObject *gen)
if (gen->gi_frame_state < FRAME_CLEARED) {
_PyInterpreterFrame *frame = (_PyInterpreterFrame *)gen->gi_iframe;

if (frame->f_lasti < 1) {
if (gen->gi_frame_state == FRAME_CREATED) {
/* Return immediately if the frame didn't start yet. SEND
always come after LOAD_CONST: a code object should not start
with SEND */
assert(_Py_OPCODE(_PyCode_CODE(gen->gi_code)[0]) != SEND);
return NULL;
}
_Py_CODEUNIT next = _PyCode_CODE(gen->gi_code)[frame->f_lasti + 1];
_Py_CODEUNIT next = frame->prev_instr[1];
if (_PyOpcode_Deopt[_Py_OPCODE(next)] != RESUME || _Py_OPARG(next) < 2)
{
/* Not in a yield from */
Expand Down Expand Up @@ -490,13 +490,11 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
// XXX: Performing this jump ourselves is awkward and problematic.
// See https://github.com/python/cpython/pull/31968.
/* Termination repetition of SEND loop */
assert(frame->f_lasti >= 0);
_Py_CODEUNIT *code = _PyCode_CODE(gen->gi_code);
assert(_PyInterpreterFrame_LASTI(frame) >= 0);
/* Backup to SEND */
frame->f_lasti--;
assert(_Py_OPCODE(code[frame->f_lasti]) == SEND);
int jump = _Py_OPARG(code[frame->f_lasti]);
frame->f_lasti += jump;
assert(_Py_OPCODE(frame->prev_instr[-1]) == SEND);
int jump = _Py_OPARG(frame->prev_instr[-1]);
frame->prev_instr += jump - 1;
if (_PyGen_FetchStopIterationValue(&val) == 0) {
ret = gen_send(gen, val);
Py_DECREF(val);
Expand Down Expand Up @@ -1344,9 +1342,8 @@ compute_cr_origin(int origin_depth, _PyInterpreterFrame *current_frame)
frame = current_frame;
for (int i = 0; i < frame_count; ++i) {
PyCodeObject *code = frame->f_code;
PyObject *frameinfo = Py_BuildValue("OiO",
code->co_filename,
PyCode_Addr2Line(frame->f_code, frame->f_lasti*sizeof(_Py_CODEUNIT)),
int line = _PyInterpreterFrame_GetLine(frame);
PyObject *frameinfo = Py_BuildValue("OiO", code->co_filename, line,
code->co_name);
if (!frameinfo) {
Py_DECREF(cr_origin);
Expand Down
2 changes: 1 addition & 1 deletion Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8980,7 +8980,7 @@ super_init_without_args(_PyInterpreterFrame *cframe, PyCodeObject *co,
if (firstarg != NULL && (_PyLocals_GetKind(co->co_localspluskinds, 0) & CO_FAST_CELL)) {
// "firstarg" is a cell here unless (very unlikely) super()
// was called from the C-API before the first MAKE_CELL op.
if (cframe->f_lasti >= 0) {
if (_PyInterpreterFrame_LASTI(cframe) >= 0) {
// MAKE_CELL and COPY_FREE_VARS have no quickened forms, so no need
// to use _PyOpcode_Deopt here:
assert(_Py_OPCODE(_PyCode_CODE(co)[0]) == MAKE_CELL ||
Expand Down
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